In the realm of automotive construction, continuous efforts are being made to lower the weight of vehicles or, while improving the features available, to prevent the vehicle weight from increasing. However, this can only be achieved by reducing the weight of certain vehicle components. Here, an effort is especially being made to greatly reduce the weight of the body-in-white in comparison to earlier car body designs. At the same time, however, more and more requirements are being made in terms of safety, especially passenger safety, in the vehicle as well as in terms of the behavior of the car body structure in case of a collision. Thus, in particular, the requirement exists that the body-in-white should weigh less while continuing to have a high or even greater strength and stiffness along with defined deformation behavior. In order to meet these requirements, car bodies are used in modern automotive construction employing components made of light metal as well as car body components made of sheet steel.
In this context, it is also a generally known procedure to make certain car body sheet steel components out of hot-worked metal sheets that exhibit a higher strength than cold-worked sheet metal components. The use of such hot-worked, high-strength or ultra-high-strength components can yield a greater strength for certain car body sections. Such hot-worked metal sheets are also referred to in automotive construction as press-hardened sheet metal components. Consequently, the expressions “press hardening” and “hot working” will be used synonymously below to refer in broad terms to sheet metal components that have greater strength in comparison to cold-worked metal sheets.
For example, the use of such hot-worked or press-hardened sheet metal components is already known from German patent DE 10 2004 037 789 B3, in which an underbody for the body of a motor vehicle has a floorpan with a foot well, a tunnel running in the lengthwise direction of the vehicle, as well as joining sections for the front and rear longitudinal chassis beams. The floorpan here is made of a one-piece, shaped sheet metal blank, whereby certain areas having a greater strength in comparison to other areas of the floorpan are provided in order to define the deformation behavior. For this purpose, the areas of greater strength are partially hot-worked as well as quenched and tempered. The areas of greater strength can be arranged in the foot well or on the tunnel. If side skirts have been are shaped onto the floorpan, these can also be hot-worked as well as quenched and tempered. The same applies to seat cross beams that are shaped in the floorpan. Those areas of the one-piece sheet metal blank onto which front or rear longitudinal chassis beams are to be attached can also be hot-worked with a rolling technique so as to acquire a higher strength. A structure similar to that of German patent DE 10 2004 037 789 B3 is also known from German patent DE 10 2004 044 925 B3.
The use of hot-worked metal sheets is also known from German patent application DE 10 2004 021 553 A1 in which a hollow longitudinal chassis beam is made up of two individual profiles, whereby the individual profiles have different strength values.
Furthermore, European patent application EP 1 382 514 A1 discloses a substructure for vehicles in which each seat cross beam of the substructure consists of a center beam profile that is arranged crosswise to the longitudinal axis of the vehicle and that, at its ends, has hat-shaped seat mounts facing in the lengthwise direction of the vehicle, whereby each seat mount that is arranged on the tunnel side is configured as a reinforcement element for the transmission tunnel and extends into the outer contour of the transmission tunnel.